The odds are against Senate Democrats this cycle. But, of course, they were against the party two years ago at this time, and Democratic Senatorial Campaign Committee Executive Director Guy Cecil didn’t merely beat the odds — he slaughtered them.

This time, Democrats face better prospects of holding onto their Senate majority next November than they did two years ago (after all, they begin with 55 seats instead of 53), but a net loss looks inevitable and a big loss is quite possible. Cecil, who is back for a return engagement this cycle, has his work cut out for him.

The biggest factor in how the cycle turns out probably isn’t candidate recruiting, fundraising or the number of open seats, though each will affect the fight for the Senate next year. It is almost certainly going to be President Barack Obama’s popularity and the electorate’s sense of how he is doing.

Democrats went into the 2012 cycle defending 23 Senate seats to the GOP’s 10 seats, and the landscape of that Senate class — races in Massachusetts and Maine, but also in North Dakota, Missouri, Virginia, Florida and Montana — certainly favored Republicans.

This cycle, the numbers aren’t quite as asymmetric, but with 21 Democratic seats and only 14 Republican seats up for election, the GOP once again begins with an advantage.

Unlike 2012, when Democrats started with at least two serious takeover opportunities, in Massachusetts and Nevada , this cycle the party lacks any good takeover opportunities (before retirements). That reality, combined with a landscape that includes a number of Democratic seats in very conservative states (West Virginia, Louisiana, Arkansas, Alaska and South Dakota), makes for an ever greater initial Democratic headache than at the start of last cycle.

With Senate contests next year in four strongly anti-Obama states, Democrats can’t afford a second Obama midterm election with a national electorate that wants to send a message of dissatisfaction with the president.

Obama carried just 35.5 percent of the vote in West Virginia, 36.9 percent in Arkansas, 39.9 percent in South Dakota, 40.6 percent in Louisiana, 40.8 percent in Alaska and 41.7 percent in Montana last year. While voters were able to split their tickets in 2012 and vote against Obama but for Democratic Senate nominees such as Joe Manchin III in West Virginia or Heidi Heitkamp in North Dakota, voters won’t be able to do the same thing in 2014.

The president isn’t on the ballot next year, so the only way for anti-Obama voters to express their opinion of the president is to vote against his party’s Senate nominees. And that makes Senate seats in anti-Obama states in 2014 much more difficult to hold than Senate seats in anti-Obama states were in 2012.

An overly ambitious — and overly liberal — agenda coming from the White House, which looks like a distinct possibility, could undermine the Democrats’ chances of holding onto Senate seats in states where Obama performed poorly in both 2008 and 2012.

Still, last year’s elections certainly proved that candidates and campaigns matter, and if all else fails for Democrats, the party can probably figure on Republican primary voters screwing up in at least a couple of states and producing nominees so weak that Democrats can steal a seat or two, as they have done during the past two elections.

You can almost see the writing on the wall in the newly open Iowa Senate race, where GOP primary voters easily could select a doctrinaire conservative over a mainstream conservative, lessening their party’s chances of picking up an already difficult opportunity.

Anyway, the cycle starts off with eight vulnerable Democratic Senate seats and not a single vulnerable GOP one. Republicans need to net six Senate seats to have a majority in the next Congress. Though not impossible, that is a very difficult task, especially given the current standing of the two parties.

At the Rothenberg Political Report, we start off by giving Republicans a slight edge in West Virginia’s open seat. South Dakota looks like a problem for Democrats with or without Sen. Tim Johnson’s retirement, while the politically conservative, anti-Obama natures of Louisiana and Arkansas put them at great risk for incumbent Sens. Mary L. Landrieu and Mark Pryor.

The cycle could deteriorate dramatically for Democrats if most or all of the next group of potentially competitive contests — Alaska, Iowa’s open seat, Montana, North Carolina and even New Hampshire — become really serious Republican opportunities. Of those five, Obama carried only two, Iowa and New Hampshire.

Obviously, this year’s special election in Massachusetts and additional retirements on both sides of the aisle could have a big effect on the final results next November.

No two cycles are exactly alike. The GOP’s failure to net three or four seats last time, as many initially expected, doesn’t mean the same will happen in 2014.

Personally I don’t believe in jinxes, whether in second-term midterms or because the Boston Red Sox sold Babe Ruth to the Yankees. But voter fatigue with a president after six years is a very real danger for Obama, and that, more than anything else, may make 2014 more challenging than last cycle for Guy Cecil.

Stuart Rothenberg (@stupolitics) is editor of the Rothenberg Political Report (rothenbergpoliticalreport.com).